The Flanders Pre Pleat AC Series 81255.042025 Non-Dusting Carbon Pleat Odor Control Filter is an odor control filter that works by activating the carbon pleat to absorb odors. It works well in commercial and industrial applications with minor odor problems. This 20" x 25" x 4" filter features low pressure resistance and a high dust holding capacity. The Pre Pleat AC filter media is constructed of polyester synthetic fiber coated in carbon. Odor producing gases become trapped in the microscopic pores of the carbon. Its media is sealed within a moisture resistant kraft board frame. The effectiveness of the odor control varies based on the type of odor or vapor removed.